Apparatus for determining the metal oxide content of an alkali liquid metal



1961 w B. HALL ET AL 3,

APPARATUS FOR DETERMINING THE METAL OXIDE CONTENT OF AN ALKALI LIQUID METAL Filed April 20, 1959 3 Sheets-Sheet 1 FIG. I.

33 INVENToHB WILLIAM BATEMAN mu.

ALAN nmyco'n BY J WW Oct. 3, 1961 w. B. HALL ETAL APPARATUS FOR DETERMINING THE METAL OXIDE CONTENT OF AN ALKALI LIQUID METAL Filed April 20, 1959 3 Sheets-Sheet 2 w Jinx '9! M Oct. 3, 1961 w. B. HALL AL 3,

APPARATUS FOR DETERMININ HE METAL OXIDE CONTENT OF AN ALKALI LIQUID METAL Filed April 20, 1959 5 Sheets-Sheet s INVENTORS W'IILIAM. BAMAN HALL AEAN DRA'YCUI'I M vq . 3,002,820 APPARATUS FOR DETERMINING THE METAL OXIDE CONTENT OF AN ALKALI LIQUID METAL William Bateman Hall, Cumberland, England, and Alan Draycott, Turrumurra, New South Wales, Australia, assignors to United Kingdom Atomic Energy Authority, London, England Filed Apr. 20, 1959, Ser. No. 807,602 Claims priority, application Great Britain Apr. 25, 1958 Claims. (Cl. 23-253) This invention relates to apparatus for determining the metal oxide content of an alkali liquid metal. I One fiactor limiting the use of an alkali liquid metal in heat transfer systems is that of compatibility of the liquid metal with the structural materials of the heat transfer system. In this connection it is known that the presence of metal oxide in the liquid metal can cause corrosionof materials which are not corroded by the liquid metal itself. It is therefore desirable to provide in a liquid metal circuit apparatus for determining the metal oxide content of liquid metal in the circuit.

According to the present invention apparatus for determining the metal oxide content of an alkali liquid metal comprises two channels each containing a barrier having orifices to permit liquid metal flow through the barrier, one barrier being resistant to corrosion by the liquid metal containing the metal oxide and the other barrier being resistant to corrosion by the liquid metal free of oxide but corroded by the metal containing the metal oxide, means for connecting the channels in parallel between two points of pressure difference in a liquid metal circuit and means for comparing the flow rates through the barriers.

By way of example, the invention will now be described with reference to the accompanying drawings wherein FIG. 1 is a line diagram, FIG. 2 is an enlarged section on the line IIII of FIG. 1, FIG. 3 is an enlarged section on the line ILL-III of FIG. 1 and FIG. 4 is a section on the line IV-lV of FIG. 3.

In FIG. 1 is shown diagrammatically part of a liquid sodium circuit incorporating apparatus for determining the sodium oxide content of the sodium flowing in the circuit. Sodium from the main sodium circuit is admitted into the lower regions of a containment tank through an inlet pipe 11 and flows into a manifold 12 through an inlet 13. From the manifold 12 sodium is fed through tubes 14 in a regenerative heat exchanger 15 and then through an annulus 16 surrounding a heater 17 into an off-centre compartment 18 through a port 19. The compartment 18 contains part of the apparatus for determining the sodium oxide content of the sodium flowing in the circuit. This part of the apparatus is shown in detail in FIG. 2 and is represented in FIG. 1 by the block 20. Sodium enters the block 20 through a valve 21 controlled by a rod 22 and is then split into two channels which connect with pipes 23, 24 having plugs (see FIG. 2) mounted on rods 25, 26. The pipes 23, 24 pass out of the block 20 and lead to an electromagnetic flowmeter 27, shown in detail in FIGS. 3 and 4. The sodium leaves the flowmeter 27 by two pipes 28 (of which only one is shown in FIG. 1) and these pipes 28 join in a manifold 29. The sodium then flows through a pipe 30 back to the heat exchanger 15 and thence to a header 32 connected with the main sodium circuit by a pipe 33. The heat exchanger 15, pipe work, flowmeter 27 etc. are contained with a cylindrical skirt 31. The sodium has a free surface 34 which is blanketed with nitrogen. The sodium flow is indicated by arrows.

Referring now to FIG. 2 the apparatus within the nited States Patent block 20 comprises two channels 35, 36 connecting at their lower ends with the pipes 23, 24 respectively and near their upper ends with a common chamber 37 into which sodium can flow through a port 38 connecting with the valve 21. Within the channels 35, 36 are plugs 39, 40 which are fixed to the rods 25, 26 and seat on shoulders 41, 42 in the channels 35, 36 respectively. Through the plugs 39, 40 there are passages 43, 44 and the plugs are each provided with three guide vanes 45, 46. Above the plugs 39, 40 are cylindrical barriers 47, 48 having orifices 49, 50 through which liquid sodium can flow to enter the passages 43-, 44. The barrier 47 is of stainless steel which is resistant to corrosion by liquid sodium and sodium oxide. The barrier 48 is of niobium which is resistant to corrosion by oxide-free liquid sodium but is susceptable to corrosion by sodium containing oxide. Initially the barriers 47, 48 are 0.02 inch thick and have 150 orifices 49, 50 which are 0.02 inch in diameter. The barriers 47 48 rest on the upper faces of the plugs 39, 40 and locate with bosses 51, 52 of a valve plate 53 which is an easy fit in an aperture 54 in the block 20. The barriers 47, 48 and plugs 39, 40 are retained by nuts and washers 55, 56 at the ends of the rods 25, 26. The nuts and washers clamp the plugs against spacing collars 66, 67 which contact the bosses 51, 52.

The valve 21, is associated with the rod 22 by a curved head 57 on the end of the rod 22 which is located in a cavity 58 between a hollow boss 59 and a nut 60 threaded to the boss 59. The valve 21 has a conical face 61 to close with a seat 62 in the valve plate 53 and has a body part 63 with three locating vanes 64 which move in a hole 65 in the plate 53.

Further description will now be made with reference to FIGS. 3 and 4 which show the fiowmeter 27 in more detail. In FIG. 3 electrical connections are omitted in order to maintain the clarity of the mechanical parts and in FIG. 4 the electrical connections are included but certain mechanical parts omitted to maintain the clarity of the magnetic and electrical parts.

A permanent magnet 68 having twin pole pairs 69, 70 and 71, 72 is suspended in a frame 73, the frame having slots 80 to fit over the pipes 23, 24 where they enter the fiowmeter thus enabling the magnet to be withdrawn. The pipes 23, 24connect with flat-Walled ducts 74, 75 in the region of the pole pairs and thence to the pipes 28. Electrodes 81 are brazed to the ducts 74, 75 and heavy current electrical conductors 7679 connect with the electrodes 81 to transit the induced in the flowing liquid metal to a remote measuring point. The assembly of magnet 68, pole pairs, ducts 74, 75 and electrodes 81 form a pair of electromagnetic flowmeters for measuring the flows of sodium in the pipes 23, 24 and hence the flows of sodium through the barriers 47, 48.

In the operation of the apparatus, connections from pipes 1i. and 33 (FIG. 1) are made to points in a sodium circuit so that a pressure difference exists be tween pipes 11 and 33 (a typical point of connection would be across one of the main pumps driving liquid metal round the main circuit) and the heater l7 operated to give a sodium outlet temperature of 600 C. The valve 21 is adjusted by the rod to give a flow through the flowmeter 21 in approximately the most sensitive range of the flowmeter and the readings of the flowmeter are taken visually or connections are made to a suitable recorder. If the sodium remains oxide-free the two readings obtained from the flowrneter (one via the stainless steel barrier 47, pipe 23 and duct 74 and the other via the niobium barrier 48, pipe 24 and duct 75) will keep substantially constant. If oxide appears, the two readings will deviate from one another as corrosion takes place in the barrier 48 so that the orifices 50 increase in size. From the flowmeter readings a graph is made by plotting against time the figure obtained by dividing the difference between flows by the sum of the flows. From the gradient .of the graph the oxide content of the sodium may be evaluated.

For maintenance purposes the plate 53 and all the valves can be removed by lifting on the rods 25, 26. A partial lift will allow sodium to pass through plugs 39, 40 to flush the surface of the barriers 47, 48.

Whilst the apparatus has been described above in relation to sodium, it may also be used with sodiumpotassium alloys or potassium.

We claim:

1. Apparatus for determining the metal oxide content of an alkali liquid metal, said apparatus comprising two channels each containing a barrier having orifices to permit liquid metal flow through the barriers, one barrier being of a material resistant to corrosion by the liquid metal containing the metal oxide and the other 20 barrier being of a material resistant to corrosion by the liquid metal free of oxide but corrosible by the metal containing the metal oxide, means for connecting the channels in parallel between two points of pressure dif- 4 ference in a liquid metal circuit and means for comparing the flowrates through the barriers.

2. Apparatus according to claim 1 wherein a plug is provided in each channel, said plugs having positions in which liquid can bypass the barriers.

3. Apparatus according to claim 1 wherein avalve is fitted in the liquid metal circuit to control liquid metal flow to the channels.

4. Apparatus according to claim 1 wherein the means for comparing the flow rates through the barriers comprises a magnet having twin pole pieces, two ducts for liquid metal located between the pole pieces, each connecting with one of the said channels in the apparatus, and electrodes attached to the ducts for transmitting induced in liquid metal when flowing in the ducts to a remote measuring point.

5. Apparatus according to claim 1 wherein one barrier is of stainless steel and the other barrier is of niobium.

Kirshenbaum Nov. 28, 1950 Werner Feb. 19, 1957 

1. APPARATUS FOR DETERMINING THE METAL OXIDE CONTENT OF AN ALKALI LIQUID METAL, SAID APPARATUS COMPRISING TWO CHANNELS EACH CONTAINING A BARRIER HAVING ORIFICES TO PERMIT LIQUID METAL FLOW THROUGH THE BARRIERS, ONE BARRIER BEING OF A MATERIAL RESISTANT TO CORROSION BY THE LIQUID METAL CONTAINING THE METAL OXIDE AND THE OTHER BARRIER BEING OF A MATERIAL RESISTANT TO CORROSION BY THE 